Method for separation, characterization and/or identification of microorganisms using mass spectrometry

A method is described to separate, characterize and/or identify microorganisms in a test sample. Said method comprises the steps of (i) lysing non-microorganism cells that might be present in the sample, (ii) separating the microorganisms as a pellet in the sample post-lysing non-microorganism cells, (iii) interrogating the pellet containing microorganisms by mass spectrometry to produce mass spectra of microorganisms, and (iv) characterizing and/or identifying microorganisms in the sample. The method may be used in characterizing/identifying microorganisms in complex samples, e.g., blood containing culture media.